mlxsw: Move Tx header handling to PCI driver

mlxsw: Move Tx header handling to PCI driver

Tx header should be added to all packets transmitted from the CPU to
Spectrum ASICs. Historically, handling this header was added as a driver
function, as Tx header is different between Spectrum and Switch-X. See
SwitchX implementation in commit 31557f0f9755 ("mlxsw: Introduce
Mellanox SwitchX-2 ASIC support"). From May 2021, there is no support
for SwitchX-2 ASIC, and all the relevant code was removed.

For now, there is no justification to handle Tx header as part of
spectrum.c, we can handle this as part of PCI, in skb_transmit().

A future patch set will add support for XDP in mlxsw driver, to support
XDP_TX and XDP_REDIRECT actions, Tx header should be added before
transmitting the packet. As preparation for this, move Tx header handling
to PCI driver, so then XDP code will not have to call API from spectrum.c.
This also improves the code as now Tx header is pushed just before
transmitting, so it is not done from many flows which might miss something.

Note that for PTP, we should configure Tx header differently, use the
fields from mlxsw_txhdr_info to configure the packets correctly in PCI
driver. Handle VLAN tagging in switch driver, verify that packet which
should be transmitted as data is tagged, otherwise, tag it.

Remove the calls for thxdr_construct() functions, as now this is done as
part of skb_transmit().

Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Link: https://patch.msgid.link/293a81e6f7d59a8ec9f9592edb7745536649ff11.1737044384.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>